A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. The top guide includes several openings, and fuel bundles are inserted through the openings and are horizontally supported by the core plate, and vertically supported by control rod guide tubes, control rod drive housings and stub tubes. Many other components, such as dryers, are located above the top guide.
A plurality of openings are formed in the bottom head dome so that components, such as control rod drives, can control components within the RPV. As an example, for a control rod drive assembly, a control rod drive housing is secured to the bottom head, and a control rod drive (CRD) is located within the housing. The CRD extends through the bottom head and engages a control rod blade (CRB). The CRB is located within a control rod guide tube (CRGT) positioned within the RPV. The CRD controls the position, or the elevation, of the CRB within the RPV.
During the lifetime of a reactor, debris may be required to be removed from within the CRGTs. During scram testing, for example, debris sometimes collects in the CRGTs, and such debris may enter into the CRD housings, which is undesirable.
In the past, and to remove debris from within the CRGTs, the top head must be removed and various other reactor components must also be removed to access the CRGTs. In addition, ropes and poles typically are utilized for manual delivery and manipulation of tools at the CRGTs. More specifically, and during reactor shut down, an operator typically stands on a bridge positioned over the open RPV and using ropes and poles, the operator positions tools adjacent the CRGTs to clean each CRGT. The ability to clean a CRGT and the quality of such cleaning greatly depends on the dexterity of the operator.
Cleaning a CRGT using known tools and methods can be time consuming and require removal of many reactor components. It would be desirable, of course, to avoid having to remove such reactor components to facilitate reducing the labor and time required to clean CRGTs.